From the prior art DE 35 46 454 C2, a double clutch transmission is known in which the output sides of two starting and shifting clutches that are arranged, one directly in front of the other, axially can be connected to the drive shaft of a drive engine. The output side of one of the two clutches is non-rotatably connected to a hollow shaft in which a shaft, that is connected to the output side of the other clutch, is supported. In addition, toothed gears for the second gear and the fourth gear are mounted on the hollow shaft, while toothed gears for the first gear, the fifth gear, the third gear and the reverse gear are mounted on the open area of the other shaft. These fixed gears, one for each gear ratio, mesh with allocated idler gears, which are arranged on an axially parallel intermediate shaft and can be connected to this shaft by way of synchronizer clutches (shifting units). Two transmission gears are allocated to each of these synchronizer clutches. The gear sequence for this transmission, based upon the double clutch, is second gear, fourth gear, first gear, fifth gear, third gear and reverse gear.
Further from DE 41 37 143 A1, a multi-stage synchronized auxiliary transmission is known in which the gear positions of two gears in each case are allocated to one of several shifting units. These shifting units are generally comprised of sliding sleeves that are axially displaceable, but non-rotatably connected to a transmission shaft which, during a shifting process, function together with synchronizer rings arranged adjacent to these sliding sleeves to brake toothed idler gears and can non-rotatably connect the idler gears to this transmission shaft.
With this known transmission, the two gears that are allocated to a single shifting unit (first gear and third gear or second gear and fourth gear) are two non-sequential transmission gears. This transmission construction is associated with the advantage that in this manner a transmission shifting system is created with which overlapping shifting activity and thus reduced shifting times are possible. It is disadvantageous, however, that a transmission of this type cannot be shifted by way of a shifting device comprising an H-shift gate as with such a gate, customarily only directly sequential transmission gears, can be shifted in the same shift track.
To overcome this problem, DE 102 53 259.1 proposed a universally configurable double clutch transmission, which is comprised essentially of a start-up assembly, a core transmission and an output assembly wherein the start-up assembly comprises a single clutch, a double clutch or a torque converter. The output assembly contains transmission components for a front-transverse drive, for a front-horizontal drive, for a rear-horizontal drive or for an all-wheel drive. The core transmission is designed as an auxiliary transmission, which is equipped with at least one input shaft, one intermediate shaft and one transmission output shaft, which is not oriented coaxially to the at least one transmission input shaft.
The gear sequence for this transmission is such that, based upon the clutch, the fourth gear is followed by the sixth gear, the second gear, the reverse gear, the seventh, the fifth, the third and the first gear. In this, the fixed gears for the fourth, sixth, second and reverse gears are non-rotatably mounted on a hollow shaft, which is connected to the output side of one of the two clutches in a double clutch, while the fixed gears of the seventh, the fifth, the third and the first gears are mounted on a shaft that is supported coaxially in the aforementioned hollow shaft and is connected to the output side of the second clutch in the double clutch.
Finally, from the unpublished German Patent Application DE 103 43 995.1, a double clutch transmission with a forward construction is known in which the idler gears for the sixth gear and for the fourth gear and the fixed gears for the second gear and the reverse gear are arranged on the transmission input shaft, which is designed as a hollow shaft, in the stated sequence. In this, between the idler gears for the sixth gear and the fourth gear, a single, common shifting unit for these gears is allocated with which they can be connected to the hollow transmission input shaft.
On the second transmission input shaft, which is supported in the hollow transmission input shaft, the fixed gears for the first gear and for the third gear and the idler gears for the fifth gear and the seventh gear are arranged in that order. The idler gears for the fifth and the seventh gear can be non-rotatably connected to the second transmission input shaft by way of a shifting unit that is common to these two gears and is positioned between them.
The intermediate shaft supports the idler gears that are allocated to the aforementioned fixed gears and the shifting units allocated to the idler gears in pairs, with known-in-the-art shifting clutches. In addition, a fixed gear is arranged on the intermediate shaft between the toothed gears of the fourth gear and the second gear, and meshes with a fixed gear on an output shaft that leads to a front-axle, differential transmission.
With this as the prior art background, the objective of the invention is to introduce a transmission structure for a double clutch transmission comprising seven forward gears and one reverse gear, which is suitable for front-horizontal installation in a vehicle and which has an output that is not coaxial to the drive. A further objective consists in that this transmission should be capable of driving the forward wheels and the rear wheels of a vehicle and, based upon its construction, it should be more cost-effective to produce than known forward construction double clutch transmissions.